The present invention relates generally to a method and apparatus for counterbalancing, and more particularly to a method and apparatus for counterbalancing a moveable visual display while achieving a low center of mass.
The use of video displays for recreational, educational, and scientific purposes has increased dramatically in recent years. Video displays are commonly used in medical operations, for example, and in many other analytical fields, to visually present a simulated environment to a user. Another particular application is in the video game industry where video displays transmit real time image data to a user. The video display is programmed to respond to actions taken by the user through a control mechanism such as a joy stick and is updated in real time.
Recently, video displays have been adapted to be secured a fixed distance in front of a user's eyes and to provide real time image data based on, for example, the movement of the user's head. Commonly known as "virtual reality", a motion sensor senses movement of the user's head and provides a signal representing the motion to a microprocessor which calculates the real time image data based on the signal.
The video display, to provide real time image data, may require a considerable amount of computing power, however. Consequently, it is difficult to design a self-contained unit secured to the user's head which is not unduly burdensome. To overcome this problem, the video display may be mechanically coupled to a boom which is fixed to a stationary frame or housing in which the processor and other components are housed.
Because the video display may have a substantial mass, it imparts a significant torque on the boom, tending to rotate the boom downward about the fixed point of rotation on the housing. In known systems, the boom is typically counterbalanced by extending the boom a significant distance beyond the rotation point on the stationary frame. U.S. Pat. No. 5,253,832, for example, discloses a suspension system which includes a boom arm counterbalanced by extending the boom arm a distance beyond the pivot point sufficient to counterbalance the weight of the viewing device. This general method of counterbalancing, however, has several disadvantages.
For example, because the counterbalancing portion of the boom extends upward from the rotation point, the center of mass of the apparatus is relatively high off the ground. This creates a significant instability in the apparatus which may cause injury to a user, particularly in the video game industry where users may "manhandle" the machine. Furthermore, because the counterbalancing portion of the boom extends upward from the rotation point, it will either be exposed above the stationary housing, or the housing will need to be extended upward to enclose the counterbalancing portion of the boom. In either case, the center of mass of the apparatus may be unacceptably high. Although the cabinet may be widened to increase its stability, the extent to which it must be widened is great enough to create other disadvantages. For example, in addition to being more cumbersome and expensive, a wide cabinet may prevent the arrangement of several machines in an island configuration.
Other known booms use gas springs to apply a counterbalancing force and work well in applying small amounts of force in one direction. However, they are not very effective at achieving a state of balance.
It would be desirable, therefore, to have a counterbalancing system that would achieve a lower center of mass, which would have the ability to balance with near zero deferential between load and counterweight, and which would limit the speed of motion of the boom.